Prime objective of this lecture is to present on Limestone. It is a sedimentary rock. It was formed mainly from sea shells. It is the compound called calcium carbonate and it is a useful raw material. Here briefly focus on What can limestone be used for? In Britain about 150 million tonnes of limestone are quarried each year.  Limestone is the compound calcium carbonate. It’s formula is CaCO3 and it can be chemically changed into other things.